There are a number of types of photorefractive surgical procedures now being used for vision correction. Included among these procedures is LASIK (Laser-Assisted In Situ Keratomileusis). LASIK is a procedure used to permanently change the shape of the cornea with an Excimer laser. A flap is cut in the cornea and folded back revealing the stroma, which is the middlesection of the cornea. Pulses from a computer-controlled Eximer laser are used to ablate or vaporize a portion of the interior of the stroma and reshape the corneal tissue. The flap is then replaced over the reshaped area to conform to the new corneal shape.
Some patients, however, are not suitable candidates for LASIK. Those patients that have extremely thin corneas are better served using a procedure other than LASIK. Advanced surface ablations techniques provide a suitable alternative in such cases. These techniques involve the removal of the very surface layer of the cornea, known as the epithelium, and lasering the exposed corneal bed. This keeps the laser from ablating or vaporizing too deep into the tissue of the cornea and reduces the risk of ectasia, or de-stabilization of the cornea.
Both LASIK and the various surface ablation techniques can be grouped under the general umbrella of laser eye surgery, but each is a little different with respect to their advantages and disadvantages. The great advantage of LASIK over a surface ablation technique, is that, as soon as the flap created during the LASIK procedure is replaced, the cornea begins to heal and will naturally seal itself to the rest of the cornea. This greatly speeds the overall healing process when compared to surface ablation techniques, which leaves the reshaped area generally more exposed or open. With surface ablation, improvement is more gradual and the eye may take a few days or even a month or two to stabilize. In general, most surgeons prefer LASIK except for patients with thin corneas, in which case a surface ablation technique is preferred. Patient satisfaction is another reason surgeons prefer LASIK, because the patient can quickly see clearly and his or her anxiety is significantly reduced.
Several potential problems are inherent in LASIK. The three most common problems are: (1) under correction, where not enough tissue is removed during the procedure; (2) over correction, where too much tissue is removed during the procedure; and (3) wrinkling of the corneal flap, where a small fold or wrinkle occurs during replacement which causes a small blurry area in the patients vision. In most cases each of these problems can be easily corrected with a second surgical procedure. Of course, if the under or over correction is very slight, the surgeon will most likely advise against any attempt to refine the patient's vision any further. In fact, many recipients of laser eye surgery, although they may never achieve normal vision, view the procedure as a success if they are able to achieve a significant reduction in their corrective-lens prescription.
In addition to the more common surgical type of problems listed above, there is also a potential for certain side effects to occur with respect to LASIK. Such side effects include dryness, blurred vision, halos around lights, increased light sensitivity, diffuse lamellar keratitis, torn flaps, incomplete flaps, and even double vision. There is also a chance that damage or scarring to the cornea can occur with the resultant partial or complete loss of vision.
Accordingly, what is needed in the art to overcome the problems set forth above is a procedure that combines the benefits of LASIK with a surface ablation technique.